In amusement rides, it has long been known to use self-propelled vehicles guided by a track or rail along a predetermined path in which passengers are exposed to a variety of entertaining views or sensations. Typically, passengers (sometimes referred to as guests) will enter and leave the vehicles while they are standing still, or travelling very slowly, and then be transported at speeds which are varied along the length of the ride. With these ride systems, it is an important consideration to maintain a safe spacing between the vehicles to avoid collisions which could frighten or injure the passengers.
Accordingly, in amusement ride systems such as those operated by the assignee of the present invention, The Walt Disney Company, a control system is necessary to control the timing intervals between the loading of vehicles, the speeds of the vehicles along the ride, and most importantly, to prevent collisions between vehicles. Since the widespread availability of computers, control systems have typically involved dividing the ride path into predetermined zones, mounting sensors and stationary brakes in association with the guide rail or track, and using a computer system to monitor the locations of all vehicles, and prevent vehicles from entering zones until preceding vehicles are clear. Because passenger safety is involved, a vehicle control system based upon external vehicle tracking sensors and a computer, must be extremely reliable. This requires redundant sensors, redundant computers, and complex failure-detecting software, all of which is very expensive to install and maintain. For example, in smaller rides, the control system can often be more expensive than the track and the vehicles.
In earlier times, before the availability of computers, there were systems for control of self-propelled vehicles moving around a track in which a mechanical arrangement was used to reduce the risk of collision between vehicles. One such system is disclosed in a 1923 patent to Lalle et al., U.S. Pat. No. 1,450,669, which discloses a plurality of vehicles moving in-line along a track, each powered by its own electric motor. In the Lalle system, each vehicle was provided with a longitudinally extending control arm, mounted for pivoting motion in a vertical plane, extending forwardly beyond the front of the vehicle. The forward end of the control arm could contact an inclined skid secured to the rear frame of the preceding vehicle, if the vehicles approached each other too closely, to pivot the control arm upwardly and thereby break the electrical circuit to the rear vehicle and cause it to stop. The control arm, at its rear end, also had a horizontal lateral branch which extended vertically down at its free end. The free end would contact a vertically movable brake rail positioned alongside the track. A ride attendant, who watched all the vehicles in motion, could elevate the brake rail, if he saw that one vehicle was approaching another with likelihood of rear end collision, thereby pivoting the control arm to disconnect power from the vehicle.
While the system disclosed in the Lalle patent may have been satisfactory for its intended purpose half a century ago, present day ride operators have demands which would not be satisfied by such a system. Reliance on visual observation of the vehicles by the ride attendant and operation of a brake rail if the attendant observed that collision was imminent would not be satisfactory for present day rides due to the large number of vehicles that may be on a single ride, the circumstance that portions of the track may pass through areas hidden from visibility of the ride attendant, and the risk that the ride attendant's attention might become distracted at a time when collision avoidance was required. Moreover, the use of a brake rail to completely stop the approaching rear vehicle would involve sequential stopping of all vehicles following the arrested vehicle to avoid sequential collisions, thus bringing the ride to a temporary halt for all vehicles following the arrested vehicle. Under current ride operation practice, it is desired to slow the rearwardly approaching vehicle down relatively to the speed of the preceding vehicle instead of bringing it to a halt, in order to keep both vehicles travelling at the speed of the forward vehicle so that the track and vehicles can handle the maximum throughput at peak periods capable of being safely achieved without collision.
The other aspect of the Lalle system, its automatic anticollision system based on the pivoted control arm contacting the skid on the preceding vehicle, would also suffer from the same problem. Namely, it depended upon disconnecting the motor of the approaching rear vehicle entirely from power rather than slowing the rear vehicle down enough to prevent collision with the preceding vehicle but allowing it to maintain its travel without coming to a halt or unduly slowing down following vehicles. Furthermore, in the Lalle system, the rearwardly facing skid on each vehicle was short and sharply inclined so that the system had no capability for varying the safe spacing between vehicles dependent upon the speed at which the forward vehicle was traveling.
As well as the complexity and cost of modern day computer dependent ride control systems and the mechanical systems such as the Lalle patent, both types of prior system are time-consuming to install on-site. This can render them unsuitable for ride systems requiring rapidity and ease of assembly and disassembly such as travelling amusement fairs.